EE35 Drivers of biodiversity decline Flashcards
what did Jared Diamond describe and what is it?
“evil quartet”
1) habitat destruction
2) introduced species
3) overkill
4) secondary extinction
Habitat loss
driven by expansion of human pop and its economy
1750- pop 791 million
1990 -pop was 563 million!
land has been converted to urban land and cropland
who wrote tragedy of the commons?
Garrit Hardin
- economic theory
- individuals behave contrary to the best interest of the common group by depleting some common resource
Overexploitation in prehistory
By humans
in prehistory- madagascar 100AD aye aye and sloth lemur
New zealand 1350AD Giant Moa
timings fit human colonisation
overexploitation that is debated
Megafaunal holocene extinction
was it humans or climate that drove giant animals to go extinct?
overexploitation in the past (known)?
American buffalo- became nearly extinct by human hunting(horses and guns) and into of bovine diseases by cattle
But has recently resurged in national parks
is there overexploition today?
what does the logistic model say we can harvest? what is the porblem with this?
Yes. theories often based on MSY around logistic model of population growing towards carryig capacity
approx- if we keep our pop rate and half carrying capacity can harvest rK/4 individuals per year
r=intrinsic rate of increase
but if harvest is more than this POPULATION CRASHES
problem with harvesting MSY?
small fluctuations / wrong estimates can cause population crashes
Why do introduced species cause biodiversity decline? examples?
increase im comp. can outcompete native
1) honeyeasters, many birds extinct now due to introduction of domestic pig,rats and mosquitos with avian disease
2) Kakapo-night parrot in new zealand now critically endangered because of intro of rats,cats,ferrets and stoats (new predators)
3)Harlequin vs Native ladybird
recent invasion in belgium and britain
what is an example of a natural experiment that shows effect of introduction of species ?
arctic fox in aleutian islands. introduced to some islands but not others early last century.Their arrival destroyed rich grasslands and left only sparse tundra.
what are secondary effects?
all wild populations od living things have complex intertwining links with other living things around them.
Give 4 examples of populations that had secondary effects on others:
1) Hippo- has insectivorous birds that feed of parasites that grow on hippos back (if hippo dies so will birds etc)
2) cattle- black drongos/cattle egrets are birsds that also feed on the cattle but this actually helps keep diseases away( destroying birds nests would lead to decrease in cattle population)
3) (past) Haast eagle fed on giant moa so they both went extinct
4) foxes on aleutian islands- knock on effec twas that sea lion population crashed and starving killer whales started eating otters and then kelp forests disappeared
what does the fuur hold wrt to temp?
predicted surface temp by 2100 will be that south pole will have the MOST increase in degrees celsius under A1 scenario
what is the millenium ecosystem assessment?
a table showing status of main threats
Where was partula turgida limited to?
Raiatea (french polynesia)
